Portable power supply



FIG. 1 is a front perspective view of a portable power supply, showing my new design;

FIG. 2 is a rear elevation view thereof;

FIG. 3 is a front elevation view thereof;

FIG. 4 is a left elevation view thereof;

FIG. 5 is a right elevation view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The broken lines shown in the drawings depict portions of the portable power supply that form no part of the claimed design. 

CLAIM The ornamental design for a portable power supply, as shown and described. 